1. Field of the Invention
The present invention relates to a method of logging subterranean reservoirs transversed by well bores. More specifically, this invention is directed to a method of logging subterranean reservoir formations employing radioactive well logging techniques and tracer injection techniques to locate and identify sand producing zones in said reservoirs.
2. Brief Description of the Prior Art
Sand-production problems and associated control methods have been recognized as a problem in the production of hydrocarbons for several decades. Sand production frequently occurs in friable, unconsolidated sandstones and appears to be directly related to rock strength of the reservoir, e.g. its degree of consolidation, and the magnitude of production rates.
Much effort has been directed to the effectiveness of remedial work in preventing the production of sand from such hydrocarbon producing reservoirs. Such methods include the injection of radioactive gravel tags during normal gravel packing procedures for the purpose of monitering the gravel pack efficiency. Another proposed method is the displacement efficiency and distribution of gravel in a reservoir rock using the "fra-Pac" method, such method employing radioactive tracer material. However, such preventive methods are being used indiscriminatively, in that many times the sections treated are unidentified and thus sections or zones are consolidated and treated which need no treatment at all. Such procedures are costly and are not always effective. Thus, the oil industry has long sought an economical, simple method to locate such sand producing zones prior to planned remedial work which would greatly increase the over-all efficiency of such work and at the same time drastically decrease total cost. However, until the present invention, there was no satisfactory method for accurately and inexpensively locating and identifying sand producing zones in friable, unconsolidated sandstone formations of a subterranean reservoir.